Vacuum distillation including predegasification of distilland



G. w. R085 ETAL 3,300,392

VACUUM DISTILLATION INCLUDING PRE-DEGASIFICATION OF DISTILLAND OriginalFiled June 1, 1962 2 Sheets-Sheet 2 INVENTORS GENE ROSS DAVID 8. R085,gMM fiwa 6W United States Patent C 3,300,392 VACUUM DISTILLATIONINCLUDING PRE- DEGASIFICATION F DISTILLAND Gene W. Ross and David S.Ross, Lorain, Ohio, assignors to Amcodyne & Co., Lorain, Ohio, an Ohiolimited partnership Continuation of application Ser. No. 199,378, June1, 1962. This application Apr. 5, 1966, Ser. No. 547,691 16 Claims. (Cl.202-176) This is a continuation of application Serial No. 199,378, filedJune 1, 1962.

This invention relates to an improved low temperature vacuumdistillation system for liquids, and in particular to an improved vacuumdistillation system in combination With an efficient prior deaeration ofthe raw liquid.

Although the invention is described herein in terms: of the conversionof impure water to fresh water, the advantages of the system apply toany liquid distillation or concentrating process where low temperatureis desirable and practical and where operative costs are an importantfactor.

' At the present time considerable effort is being directed to theproblem of producing fresh water from sea water or other contaminatedsources in a practical and economical manner. As is known, naturallyfresh water, is being depleted in some parts of the United States, andin other parts the only readily available water is sea water. Theprimary goal in the field of fresh water production is the conversion ofraw water, whether it be sea water, brackish water, or watercontaminated with industrial or sewage .waste, at a cost which iscomparable to that of presently available fresh, pure water.

Obviously, a number of workable processes for producing fresh water fromraw sea water or brackish water are known, one of the simplest, intheory at least, being the distillation of the raw water andcondensation of the vapor. The problems associated with the evaporationof large amounts of water such as would be needed to supply a city arewell known. It has long been known that the presence of dissolved gasesin raw water reduces the efficiency of the still and causes corrosion inthe water handling equipment. At temperatures above 150 F. the scaleforming chemicals are released from the raw water and coat the heattransfer surfaces. This reduces the efficiency of the transfer of heatinto the water and thereby adds considerably to the already high heatrequirements of a conventional evaporation process. Corrosion of theequipment obviously adds to the cost of the prodnot by requiringconstant replacement, shutdown of the system or the use of expensivematerials of construction. Various vacuum distillation processes havebeen suggested and used in an attempt to reduce the scaling andcorrosion by operating at temperatures below the atmospheric boilingpoint. A major problem encountered is the high cost of operatingconventional vacuum pumping equipment to produce and maintain the vacuumrequired to operate the still. In some cases the same problem existswith respect to producing and maintaining the vac- .uum required tooperate ambient temperature deaerating equipment used to .treat the rawwater prior to entry to the still.

The present invention overcomes the above disadvantages by providing anovel combination of an eflicient "ice tern contemplated in theinvention is applied to the still so that the deaerated water therein issubstantially at its boiling point. A closed cycle gas compression andexpansion system, similar to a refrigeration system, is provided in thedistillation system to supply the latent heat of vaporization to thedeaerated raw water and to condense the vapor thus formed by absorbingthe same amount of heat.

It is the primary object of the present invention to provide an improvedprocess and apparatus for distilling raw or impure liquid and condensingthe vapors whereby a pure distillate is obtained at low cost ofequipment and power consumption.

It is a further object of this invention to provide an improved low-costprocess and apparatus for distilling raw liquid which includes anefficient, low-cost deaeration of the raw liquid thus reducing thecorrosion problem within this apparatus.

It is a further object to provide a low-cost distillation system whichincludes a closed cycle gas compression and expansion system as themeans for supplying and absorbing heat in the evaporation andcondensation parts, respectively, of the distillation system.

It is a further object to provide a low-cost efiicient distillationsystem which operates at near ambient temperatures thereby reducing heatlosses and the formation of harmful scale.

These and other objects will become apparent from a reading of thefollowing description of several embodiments of the invention when takenin conjunction with the drawings in which:

FIGURE 1 is a diagrammatic side elevational view, partly in section of asea-water conversion system embodying the principles of the presentinvention;

FIGURES 2, 3 and 4 are diagrammatic elevational sectional views of thedeaerator of FIGURE 1 illustrating the operation of the same; 1

FIGURE 5 is a diagrammatic elevational view of a slightly differentdeaerator suitable for use in the system of the invention;

FIGURE 6 is a diagrammatic elevational view of a modification of thesystem of FIGURE 1; and

FIGURE 7 is a diagrammatic elevational view of another deaer-ato-r incombination with the still of FIG- URE 1.

Referring to FIGURE 1, it is seen that a fresh water producing systemembodying the principles of the present invention includes as its majorcomponents, a deaerator 10, a vacuum still 12 and a closed gascompression and expansion circuit 14. Raw water contaminated withdissolved gases, for example sea water, enters the deaerator 10 throughan inlet pipe 16 from a source (not shown) and after deaeration isdischarged from the deaerator 10 through a pipe 18 which connects withthe bottom of the still 12 through heat exchangers 20 and 22. A vacuumline 24 leads from the deaerator 10 to the condensing portion of thestill 12 to maintain a vacuum in the latte-r.

Concentrated brine is pumped by a brine pump 26 from the evaporatingportion of the still 12 through a pipe 28 to the heat exchanger 22 andthen to waste through line 29. Distilled fresh water is pumped by adistillate pump 30 from the still 12 through a pipe 32 to the heatexchanger 20 and then to storage through a line 31.

A preferred construction of a suitable deaerator is that illustrated inFIGURES 1 through 4, it having been found that this construction willreduce the dissolved oxygen gas content of raw water to less than 0.5part oxygen per million parts of water. As shown, the deaerator 10includes integral upper and lower chambers 34 and 36, respectively,separated by a solid horizontal partition 38 positioned so as to makethe capacity of lower chamber 36 greater than that of the upper chamber34.

The upper and lower chambers are in communication through a pipe 40which connects the lower portion of lower chamber 36 to any convenientportion of upper chamber 34. In the lower portion of pipe 40 is a pump42, such as a centrifugal pump, adapted to pump liquid from thelower'chamber 36. Upstream of pump 42 is a three-way valve 44 which isadapted to direct fluid in pipe 40 into deaerator discharge pipe 18 orinto the upper chamber 34 through section 46 of pipe 40. As illustrated,valve 44 is a diaphragm valve which is responsive to the pressure inupper chamber 34. A small tube 48 connects the upper chamber with oneside of a conventional diaphragm actuator 50 whereby pressures in excessof a predetermined figure place pipe 40 in communication with pipe 18and pressure below the predetermined figure place pipe 40 incommunication with the upper chamber 34.

The upper and lower chambers of the deaerator are in communication attheir junction through a downcomer 51 containing a second diaphragmvalve 52 which is responsive to the pressure in pipe 40 upstream of pump42. As seen in the drawings, a small tube 54 connects pipe 40 with aconventional diaphragm actuator 56 whereby valve 52 closes and openswith an increase and decrease, respectively, in pressure in pipe 40.

The upper and lower chambers 34 and 36 are further in communicationthrough a pipe 58 connecting the top portion of lower chamber 3 6 withthe top portion of upper chamber 34. A check valve 60 in pipe 58 permitsfluid flow only from the lower to the upper chamber.

Upper chamber 34 is also provided with a gas vent pipe 62 connecting theupper portion of the chamber with the atmosphere. A check valve 64 inpipe 62 permits flow only from the chamber to the atmosphere. Upstreamof check valve 64 is a thermodynamic check 66 of known constructionwhich remains open so long as only gas flows therethrough but whichcloses when liquid begins to pass therethrough as a result of the actionof flowing liquid on the device. The raw water inlet pipe 16 connectswith upper chamber 34 and is provided with a flow control valve 68.

A liquid level responsive device, such as a conventional liquid levelelectrode, illustrated at 70, is provided in the lower portion of thepipe 58 and operates through a suitable control circuit (not shown) tostart pump 42 when the electrode 70 becomes immersed in liquid. Thelower chamber 36 is also provided with a liquid level responsive device,illustrated at 72 and similar to electrode 70 which operates through asuitable control circuit (not shown) to stop pump 42 when the electrode70 is not immersed in liquid. Electrode 70 should be located at or abovethe connection between inlet pipe 16 and chamber 34 so that raw waterflowing into the deaerator will not actuate the pump 42 until after thelower cham- 'ber 36 has been filled, as seen in FIGURE 1. Electrode 72should be located above the inlet of pump 42 so that a positive head ofwater is applied to the pump inlet at all times.

Lower chamber 36 may also be provided with means for agitating theliquid therein to aid in the liberation of dissolved gases from the rawwater. As shown, a suitable agitating means may take the form of waterjets 74 to which water from the discharge of pump 42 is fed through apipe 75. It is also contemplated that chamber 36 may be partially orentirely filled with Raschig rings or other material for increasing thefree surface area of the liquid in the chamber 36.

The vacuum still 12 includes a leak-proof tank 76, preferably elongatedin a vertical direction, and an internal tray-like structure forcollecting condensed fresh water such as an inclined baflle 78 securedto the walls of the tank 76. The baffle 78 should be positionedgenerally below the coils 92 although its precise position and its shapeand size may vary so long as its watercollecting function is retained.

Distillate pipe 32 connects with the still tank 76 at any location whichplaces the pipe in communication with liquid collected by baffle 78.Pump 30, such as a centrifugal pump, in the product pipe 32 should bebelow the level of liquid on baflie 78 so that a positive head of liquidmay be maintained on the pump inlet. Discharge pipe 18 from thedeaerator 10 conects with the heating portion of the still tank 76 so asto effectively condense the hot gas in the coil 90. The brine dischargeline 28 is connected to the still tank at a location below the liquidlevel therein. Preferably, a baffle 79 or other arrangement will resultin brine being drawn off from the upper portion of the liquid in thetank. Vacuum line 24 connects with the upper portion of tank 76 at alocation which is outside thel water-collecting pocket formed by baffle78 and which is so related to cooling coil 92 that vapors are notwithdrawn. A check valve 80 in line 24 permits fluid flow only into thedeaerator 10.

The still 12 may also be provided with a liquid level responsive device,illustrated at 82, which through a suitable control circuit, illustratedby dotted line 84, operates the raw water inlet valve 68 to thedeaerator. The device 82 is located at the desired liquid level in tank76 and actuates valve 68 thus regulating the flow of raw water into thedeaerator 10 and maintaining a relatively constant liquid level in thestill tank 76.

The gas compression system 14 includes a mechanically driven blower, orcompressor 86 and a sealed line 88 leading from the blower outletthrough the still 12 back again to the blower inlet. Line 88 includestwo coiled heat-transfer sections 90 and 92 positioned in the heatingand condensing portions of the still tank 76, respectively. Thecondenser coils 92 are positioned above baffle 78 so that condensatedripping from their exterior surfaces will be collected by the baffle.The heating coils 90 are positioned in any manner so as to be immersedin the liquid in the heating portion of the still. The size, shape, andnumber of the coils will vary depending on the capacity of the still,the temperatures involved and in such a way as to provide for eflicientheat transfer.

In the operation of the water conversion system illustrated in FIGURE 1,the deaerator 10 functions to provide deaerated water to the still 12and simultaneously to maintain a vacuum in the still. The operation ofthe deaerator is cyclic and is fully illustrated in FIGURES 1 through 4each of which illustrates a step in a complete deaeration cycle.

In FIGURE 1, the deaerator 10 is receiving a charge of raw water throughraw water inlet pipe 16 from a source (not shown) under the action of avacuum in the deaerator or by means of a pump (not shown) in pipe 16 orby means of gravity if the source is elevated above the deaerator. Thewater passes from pipe 16 over partition 38, through valve 52 into thelower chamber 36, and continues to rise until its level reacheselectrode 72. Electrode 72 then actuates pump 42.

As seen in FIGURE 2 pump 42 then begins discharging the raw water tothe'upper chamber 34 through pipe 40 and valve 44. Simultaneously, valve52 is closed by the pump discharge pressure whereby displacement of thewater from the lower chamber 36 results in a high vacuum in thatchamber. The actual pressure realized in lower chamber 36 isapproximately the vapor pressure of the water in the chamber and thuswill vary with the water temperature. In practice, a vacuum of about 29inches of mercury is realized with water at about 70 F.

At this vacuum, particularly if the water is agitated by the upperchamber 34 reaches valve 66, the kinetic energy of the water causes thevalve to close. The pressure in the upper chamber then rises as theresult of continued operation of pump 42 and causes the 3-way valve 44to direct water from the lower chamber 36 into pipe 18 leading to thevacuum still 12. Pump 42 continues to operate until the water level inthe lower chamber 36 drops to below electrode 72.

It is apparent that only highly deaerated water is discharged into pipe18, because the first fraction of water removed from the lower chamberis retained in the upper chamber. Obviously, this first fractioncontains some dissolved gases not only because it has not been subjectedto a vacuum for as long a time as the later fraction, but also becauseit may pick up additional gas when discharged into the upper chamber. Itis apparent, however, that this partially deaerated fraction is returnedto the lower chamber 36 for further deaeration in the next cycle. Thus,the water discharged through pipe 18 has, in part, been subjected to anumber of deaeration cycles and contains substantially no dissolvedgases. As noted previously, this is extremely important if corrosion isto be avoided in the still 12. It has been found by chemical analysis ofthe discharge from this deaerator that the oxygen content of raw watercan be reduced to about 0.2 to 0.4 part per million.

FIGURE 4 illustrates the action of the deaerator after pump 42 has beenstopped by electrode 72. The lack of pump pressure causes valve 52 toopen whereupon the water in the upper chamber 34 flows by gravity intothe lower chamber 36, and the liberated gases in the lower chamber 36are displaced through pipe 58 and check valve 60 into the upper chamber34. At this point the apparatus is ready to receive another charge ofraw water and to begin again the operation illustrated in FIGURE 1.

' Since both chambers are at a vacuum the next charge of raw water canconveniently be drawn into the apparatus merely by opening valve 68. Asseen in FIGURE 1, valve 68 may conveniently be operated by controlcircuit 82 in response to the level of water in the still 12.

The deaerated raw water from the deaerator is partially evaporated instill 12 at only slightly higher temperature thanit leaves thedeaerator. This is accomplished by maintaining the still at a vacuumsuch that the water therein is substantially at its boiling point andneeds only to have added to it the latent heat of vaporization.According to the invention, the vacuum is drawn on the still 12 byconnecting the still with the lower chamber 36 of the deaerator 10 bymeans of line 24. As

it is apparent from the preceding description of the would remainetfective because no gas is intended to enter the still. As a practicalmatter, some gas may enter the still as a result of leaks or temporarymalfunction of the deaerator and thereby tend to destroy the vacuum. Thecyclic vacuum pulled through line 24 not only as- .sures a vacuum in thestill but also assures that any gas which reaches the still will not bepermitted to remain and thereby cause corrosion parts of the still.

The operation of the gas compression and expansion cycle 14 to vaporizethe deaerated water and to condense the vapors is analogous to that of aconventional refrigeration system. The refrigerant may be one having aboiling point slightly below that of the water in the still 12, iscompressed by blower 86 and thereby heated to above the temperature ofthe water in the still. When passed through coils 90 in the heatingportion of the still, the hot compressed gas gives up its latent heat ofvaporization to the water in the still and is condensed to a liquid.Simultaneously, some of the water in the still is vaporized.

The liquified refrigerant then passes to coils 92 in the condensingportion of the still where it vaporizes by absorbing the latent heat ofvaporization of the water vapor in the still. Some of the water vapor isthereby condensed on the coils 92 and runs off onto the baffle 78 whereit is collected. The vaporized refrigerant returns to the blower 86 andis again compressed. The theoretical work or heat of compression appliedto the refrigerant by the blower is that required (1) to overcome theresistance of the complete refrigerant circuit, (2) to maintain economical design temperature differences between heating and condensing coilsand (3) to replace equipment heat losses and heat lost from the systemas a result of heat gain by the product and brine streams.

Theoretically, it is possible to vaporize the water in the still andcondense the vapors at the same temperature by supplying and absorbingonly the latent heat of vaporization at the boiling point of the water.This optimum condition is desirable because the distillation can becarried out at the temperature of the raw water and thus avoid theexcess heat losses. However, since the optimum condition cannot beobtained because of fluctuations in raw water temperature and in theeconomical heat transfer characteristics of the coils 90 and 92 andother variables, some increase in water temperature occurs in the still.In order to conserve the heat as much as p0ssible,'both the productwater and. the concentrated brine discharged from the still are passedin heat-exchange relationship with the deaerated water in pipe 18. Sincethe product water in pipe 32 is slightly cooler than the brine in pipe28, the incoming water in pipe 18 is first heated by the product waterin heat exchanger 20. Since the still is under a vacuum, pumps 26 and 30are required to discharge the brine and product water to the atmosphere.

The ratio of product water flow in pipe 32 to brine flow in pipe 28 ispreferably maintained as high as possible in order to reduce the amountof heat discarded with the brine. Obviously, however, the concentrationof the brine must not be permitted to rise to the level at which solidswill be precipitated in the still or heat exchanger 22. The flow figuresand temperatures noted on the flow sheet of FIGURE 1 are indictaive ofapproximate values obtainable with the system but are not intended to bethermodynamically precise. It will be seen that the heat losses in thesystem are very small not only because the distillation equipment may beoperated at approximately 92 F., but also because the dischargetemperature of product water and brine is only five degrees higher thanthe raw water temperature. Even more important in the saving of powerconsumption in the present system is the relatively small mechanicalenergy required to operate the pumps 26, 30 and 42 and the blower 86. Ithas been calculated that for a system producing 1,000 gallons/hr. offresh water from 1,250 gallons/hr. of raw water, the pumps require nomore than 5 hp. The blower requires only about 40 hp. when operating ata pressure differential of about 3 p.s.i. with a suitable refrigerantsuch as one of the Freons.

A somewhat different form of deaerator suitable for use in the waterconversion system of the present invention is illustrated in FIGURE 5wherein primed reference numerals are used for similar parts. Thedeaerator 10', like the one previously described, includes integralupper and lower chambers 34' and 36', respectively, separated by ahorizontalpartition 38' positioned so as to give the lower chamber 36'greater capacity than the upper chamber 34'.

A pipe 40 connects the upper and lower chambers 34 and 36' and includesa pump 42 in its lower portion for discharging liquid from the lowerchamber 36. A check valve 94 permits flow through the pipe 40 only fromthe lower chamber. The upper and lower chambers 34' and 36' of deaerator10' are in communication at their junction through a diaphragm valve 52which is made responsive to the pump discharge pressure by means of tube54. The chambers are further in communication through a pipe 58 providedwith a check valve 60' and a liquid level responsive device 7 The upperchamber 34 is provided with a gas vent 62 having check valve- 64 andliquid check 66'. Deaerator discharge pipe 18' connects directly Withthe lower portion of the upper chamber 34 and is provided with aspring-loaded valve 96 which is adapted to open When the pressure in theupper chamber exceeds a predetermined value.

A raw water inlet pipe 16' containing a valve 68' connects with thelower portion of the lower chamber 36' rather than with the upperchamber as in deaerator in FIGURES 1-4. A liquid level responsive device72' is provided in chamber 36 for stopping pump 42' and a vacuum line 24including a check valve 80 is provided for drawing a vacuum on the still12.

The operation of deaerator 10' is similar to that of the deaerator 10 ofFIGURES 14 except that some of the first fraction of water removed fromthe lower chamber 34' opens spring-loaded valve 96 in pipe 18' so thatdeaerated water may be delivered to the still 12. When the water leveldrops to electrode 72', pump 42' is stopped, valve 52 opens, and thewater remaining in the upper chamber 34 flows by gravity into the lowerchamber 36'. The apparatus is then ready to receive another charge ofraw water from pipe 16.

The deaerator 10 may be substituted for deaerator 10 in the system ofFIGURE '1 merely by connecting pipes 18 and 24 to the still 12 in thesame manner as are pipes 18 and 24.

FIGURE 6 illustrates a modification of the system of FIGURE 1 wherein anaccumulator tank 98 is connected between the deaerator 10 and the still12. As shown, deaerator discharge pipe 18 is connected to the lowerportion of the accumulator 98, and vacuum line 24 is connected to thetopportion thereof. Pipe 18a and line 24a connect the accumulator 98 withthe still so as to deliver water and to draw a vacuum as describedpreviously. Raw water inlet valve 68 in pipe 16 may conveniently beoperated in response to the water level in the accumulator 98 by asuitable control circuit 100 so as to maintain the level in theaccumulator relatively constant. The delivery of water to the still maybe made responsive to the water level in the still by means of a valve102 in pipe 18a and a suitable control circuit 104. In this arrangement,even better deaeration of the raw water may be achieved as a result ofthe additional time that the water is maintained under vacuum. Further,the cyclic discharge of deaerated water through pipe 18 is compensatedfor.

FIGURE 7, in which double-primed numerals identify elements similar tothose already described, illustrates a further embodiment of a deaeratorin combination with a vacuum still 12" identical with that of FIGURE 1.In this embodiment the deaerator is a single, uncompartmented tank 106having an inlet pipe 16", and an outlet pipe 18" and an upper vent pipe62" provided with a .check valve 64". A pump 112 in the inlet pipe 16"provides positive feed to the tank from a raw water source (not shown)and a valve 113 in the pump discharge per mits the tank 106 to be sealedfrom the raw water source when desired. A pair of vertically spacedliquid level electrodes 116 and 118 within the tank 106 are providedwith a suitable control circuit 114 leading to the pump 112 so as tomaintain a desired water level within the tank. A pump 108 in thedischargeqline 18 provides positive discharge from the tank 106 and acheck valve 120 in the pump inlet permits liquid flow only in the dis.-charge direction.

The deaerator tank 106 may be provided with jets or other agitatingmeans for the liquid therein and may contain Raschig rings or othermeans for increasing the free liquid surface. The system of FIGURE 7 mayalso in,-

clude a vacuum accumulator tank between the tank 106 and the still 12"in the manner described with respect to FIGURE 6.

In operation, the deaerator of FIGURE 7 is filled with raw water to thelevel of electrode 118 by opening valve 113 and operating the inlet pump112. The valve 113 is then closed either manually or by a suitablecontrol system which takes its signal from, for example, electrode 118.The discharge pump 108 is then operated to begin pumping water throughdischarge pipe 18" and heat exchangers 20 and 22" to the vacuum still12". A boiling point vacuum is simultaneously formed in the tank 106whereby dissolved gases are liberated from the water therein. When theliquid level in the still 12" rises to a predetermined level the pump108 is stopped by means of a control circuit 110. When the water levelin the tank 106 drops to below electrode 116, the valve 113 is openedand the pump 112 is automatically actuated to feed more water into thetank. The gases liberated in the tank during operation of the dischargepump 108 are forced out the vent 62" during this operation.

A vacuum line 24" leading from the deaerator tank 106 to the top of thestill 12" draws a vacuum in the still during operation of the pump 108and a check valve in the line 24" prevents loss of a vacuum in the stillduring operation of the inlet pump 112. As in the operation of the stillof FIGURE 1, distilled product water is removed through a pipe 32" by apump 30" and is passed through the heat exchanger 20 to transfer some ofits heat to the deaerated water being fed to the still. Brine is removedthrough pipe 28" by pump 26" and is passed through heat exchanger 22"before being discharged to waste.

Thus it will be appreciated that a novel, efi'icient and economicalsystem for distilling liquids while avoiding corrosion and scaleformation has been devised. While several modifications of the inventionhave been described in terms of the treatment of raw water, it is notintended that the invention should be limited to the treatment of anyparticular liquid or to the details of the disclosed embodiments exceptas they appear in the appended claims.

What is claimed is:

1. Apparatus for evaporating a liquid and condensing the vapors thereofcomprising:

diquid degasifying means including scalable tank means for enclosing acharge of liquid and an overlying vapor portion, vent means incommunication with the interior of said tank means above the charge ofliquid and including valve means for alternately sealing and unsealingsaid tank means, liquid pumping means operable at a high liquid level insaid tank means to pump liquid out of said tank means when said tankmeans is sealed thereby producing degasified liquid by producing avacuum in said tank means to cause dissolved gases to be liberated fromliquid remaining in said tank means and to be collected in overlyingrelationship to said remaining liquid, means for intermittentlyintroducing additional liquid into said tank means thereby displacingpreviously liberated gases through said vent means;

still means having a liquid receiving chamber and a vapor retainingchamber communicating therewith; transfer means including a conduit anda valve for intermittently withdrawing said degasified liquid from saidtank means and for transferring the withdrawn degasified liquid to saidliquid receiving chamber;

means for continually maintaining said vapor retaining chamber undervacuum including a conduit interconnecting said vapor retaining chamberand said tank means and a valve in said conduit connected to pass gasonly from said vapor retaining chamber to said tank means;

heating means associated with said liquid receiving chamber forevaporating liquid therein;

cooling means associated with said vapor retaining chamber forcondensing vapor from said liquid receiving chamber;

means for collecting and withdrawing condensed vapor from said vaporretaining chamber;

and means for withdrawing unvaporized liquid from said liquid receivingchamber.

2. Apparatus for evaporating a liquid and condensing the vapors thereofcomprising: liquid degasifying means including vapor-tight tank meansfor enclosing a charge of liquid and an overlying vapor, means forsealing the overlying vapor in the tank means to establish saidvaportight tank means and liquid pumping means for pumping liquid out ofsaid tank means thereby lowering the pressure in said tank means tocause dissolved gases to be liberated from liquid in said tank means;still means having a liquid receiving chamber and a vapor retainingchamber communicating therewith; means for conducting the saiddegasified liquid from said tank means under liquid level control insaid tank means to said liquid receiving chamber; means for continuallymaintaining said vapor retaining chamber under vacuum including aconduit interconnecting said vapor retaining chamber and said tank meansand a valve in said conduit connected to pass gas only from said chamberto said tank means; heating means associated with said liquid receivingchamber for evaporating liquid therein; cooling means associated withsaid vapor retaining chamber for condensing vapor from said liquidreceiving chamber; means for collecting and withdrawing condensed vaporfrom said vapor retaining chamber; and means for withdrawing unvaporizedliquid from said liquid receiving chamber.

3. Apparatus as in claim 1 further comprising: means for introducingliquid into said tank means; and means responsive to liquid level insaid still means for controlling said introducing means.

4. Apparatus as in claim 1 further comprising; means for introducingliquid into said tank means; means responsive to the liquid level insaid tank means for controlling said introducing means; means responsiveto the liquid level in said still means for controlling the flow ofliquid from said tank means to said still means through said transfermeans.

5. Apparatus as in claim 1 wherein said means for transferringdegasified liquid from said tank means to said still means includes anaccumulator tank for storing degasified liquid, said accumulator tankbeing connected to said tank means and to said still means by conduitswhich conduct the degasified liquid, said accumulator tank having avapor containing portion and a liquid containing portion; and means formaintaining the interior of said accumulator under vacuum, said meansincluding valve means connected between said tank means and the vaporcontaining portion of said accumulator tank for passing gas only fromsaid vapor containing portion to said tank means.

6. Apparatus as in claim 5 further comprising: means responsive to theliquid level in said still means for controlling the fiow of degasifiedliquid through the conduit from said accumulator tank to said stillmeans.

7. Apparatus as in claim 1 further comprising; means for passing liquidwithdrawn from said still means in heat exchange relationship withliquid delivered to said still means.

8. Apparatus as in claim 1 wherein said heating and cooling meansinclude a compressor for a refrigerant gas and a closed conduitextending from said compressor to said liquid receiving chamber of saidstill means then to said vapor retaining chamber and then back to saidcompressor.

9. Apparatus as in claim 1 further comprising: agitator means in saidtank means for agitating liquid therein.

10. Apparatus for evaporating a liquid and condensing the vapors thereofcomprising: means for degasifying the liquid prior to evaporationincluding:

means defining first and second chambers, said second chamber beingabove said first chamber, conduit means for delivering liquid to saidfirst chamber, liquid pumping means having its inlet in communicationwith said first chamber below the level of liquid therein and its outletin communication with said second chamber whereby operation of saidliquid pumping means produces a boiling point vacuum in said firstchamber for degasifying liquid therein and delivers liquid to saidsecond chamber, valve means between said chambers; means responsive toopera tion of said liquid pumping means for closing said valve means,and check valve means connected between said chambers for passing fiuidonly from said first chamber to said second chamber;

a still having a liquid vaporizing portion and a vapor condensingportion, said still including:

collecting means for distilled liquid therein; a liquid outlet fordischarging distilled liquid, a liquid outlet for dischargingundistilled liquid, said still having its vaporizing portion incommunication with said second chamber whereby deaerated liquid may bedelivered to said still, and its condensing portion in communicationwith said first chamber through valve means connected to pass gas fromsaid condensing portion whereby a vacuum may be drawn in said still;

and means for supplying and absorbing heat in order to evaporate liquidand condense vapors within said still including:

a heating conduit in said vaporizing portion of said still, a coolingconduit in said condensing portion of said still, and gas compressingmeans, said heating conduit, said cooling conduit and said compressingmeans being interconnected in a closed circuit.

11. Apparatus as in claim 10 further comprising: heat exchanger meansconnected between the outlet of said liquid pumping means and saidvaporizing portion of said still for passing liquid delivered to saidstill in heat exchange relationship with liquid discharged from saidstill.

12. Apparatus as in claim 10 including first heat exchanger meansfurther connected to said distilled liquid outlet in said still andsecond heat exchanger means further connected to said undistilled liquidoutlet in said still.

13. Apparatus as in claim 10 further comprising: valve means in saidconduit means for delivering liquid to said first and second chambers,and means responsive to liquid level in said still for controlling saidvalve means.

14. Apparatus as in claim 10 further comprising: an accumulator tankconnected by conduits to said still and to said second chamber andhaving a vapor containing portion and a liquid containing portion, saidcheck valve means being connected in the conduit between said vaporcontaining portion and said first chamber; and a conduit connecting saidvapor containing portion with said condensing portion of said still, andsaid vapor containing portion being in communication with said pumpmeans inlet and with said condensing portion of said still.

15. Apparatus as in claim 10 further comprising: agitator means in saidfirst chamber for agitating liquid there- 16. Apparatus for evaporatinga liquid and condensing the vapors thereof comprising: means fordegasifying the liquid prior to evaporation including:

means defining first and second chambers, said second chamber beingabove said first chamber, conduit means for delivering liquid to saidfirst chamber, liquid pumping means having its inlet in communicationwith said first chamber below the level of liquid therein, and itsoutlet in communication with said second chamber through a flowdistribution valve means whereby operation of said liquid pumping meansproduces a boiling point vacuum in said first chamber for degasifyingliquid therein said first chamber whereby a vacuum may be drawn anddelivers liquid to said second chamber, valve in said still;

means between said chambers; means responsive to and means for supplyingand absorbing heat in order to operation of said liquid pumping meansfor closing evaporate liquid and condense vapors within said still saidvalve means and valve means connected be- 5 including:

tween said chambers for passing fluid only from said a heating conduitin said vaporizing portion of said first chamber to said second chamber;still, a cooling conduit in said condensing portion of a still having aliquid vaporizing portion and a vapor consaid still, and gas compressingmeans, said heating densing portion, said still including: conduit, saidcooling conduit and said compressing collecting means for distilledliquid therein; a liq- 10 means being interconnected in a closedcircuit.

uid outlet for discharging distilled liquid, a liquid outlet fordischarging undistilled liquid, said still No references citedhaving itsvaporizing portion in communication with said flow distribution valvemeans whereby deaerated NORMAN YUDKOFF Primary Exammerliq i y bedelivered y said liquid p pi is F. E. DRUMMOND, Assistant Examiner.means from said first chamber to said still, said still having itscondensing portion in communication with

1. APPARATUS FOR EVAPORATING A LIQUID AND CONDENSING THE VAPORS THEREOFCOMPRISING: LIQUID DEGASIFYING MEANS INCLUDING SEALABLE TANK MEANS FORENCLOSING A CHARGE OF LIQUID AND AN OVERLYING VAPOR PORTION, VENT MEANSIN COMMUNICATION WITH THE INTERIOR OF SAID TANK MEANS ABOVE THE CHARGEOF LIQUID AND INCLUDING VALVE MEANS FOR ALTERNATELY SEALING ANDUNSEALING SAID TANK MEANS, LIQUID PUMPING MEANS OPERABLE AT A HIGHLIQUID LEVEL IN SAID TANK MEANS TO PUMP LIUQID OUT OF SAID TANK MEANSWHEN SAID TANK MEANS IS SEALED THEREBY PRODUCING DEGASIFIED LIQUID BYPRODUCING A VACUUM IN SAID TANK MEANS TO CAUSE DISSOLVED GASES TO BELIBERATED FROM LIQUID REMAINING IN SAID TANK MEANS AND TO BE COLLECTEDIN OVERLYING RELATIONSHIP TO SAID REMAINING LIQUID, MEANS FORINTERMITTENTLY INTRODUCING ADDITIONAL LIQUID INTO SAID TANK MEANSTHEREBY DISPLACING PREVIOUSLY LIBERATED GASES THROUGH SAID VENT MEANS;STILL MEANS HAVING A LIQUID RECEIVING CHAMBER AND A VAPOR RETAININGCHAMBER COMMUNICATING THEREWITH; TRANSFER MEANS INCLUDING A CONDUIT ANDA VALVE FOR IN TERMITTENTLY WITHDRAWING SAID DEGASIFIED LIQUID FROM SAIDTANK MEANS AND FOR TRANSFERRING THE WITHDRAWN DEGASIFIED LIQUID TO SAIDLIQUID RECEIVING CHAMBER; MEANS FOR CONTINUALLY MAINTAINING SAID VAPORRETAINING CHAMBER UNDER VACUUM INCLUDING A CONDUIT INTERCONNECTING SAIDVAPOR RETAINING CHAMBER AND SAID TANK MEANS AND A VALVE IN SAID CONDUITCONNECTED TO PASS GAS ONLY FROM SAID VAPOR RETAINING CHAMBER TO SAIDTANK MEANS; HEATING MEANS ASSOCIATED WITH SAID LIQUID RECEIVING CHAMBERFOR EVAPORATING LIQUID THEREIN; COOLING MEANS ASSOCIATED WITH SAID VAPORRETAINING CHAMBER FOR CONDENSING VAPOR FROM SAID LIQUID RECEIVINGCHAMBER; MEANS FOR COLLECTING AND WITHDRAWING CONDENSED VAPOR FROM SAIDVAPOR RETAINING CHAMBER; AND MEANS FOR WITHDRAWING UNVAPORIZED LIQUIDFROM SAID LIQUID RECEIVING CHAMBER.